1. Technical Field
The present invention relates to a method and composition for remediating subsurface contaminants from soil and groundwater, and more specifically, the present invention describes a method and composition for the in situ remediation of contaminants through the administration of a composition including a biochar and an oxidizing agent, wherein the biochar is both an absorbent medium and a catalyst for the oxidation of organic contaminants.
2. Background Art
The discharge of organic compounds and other contaminants into the soil and surface water can lead to contamination of surface and groundwater sources resulting in potential public health impacts. Treatment of such wastewater and the remediation of soils and groundwater contaminated with organic compounds and other contaminants has been expensive, require considerable time, and in many cases are incomplete or unsuccessful.
Many different physical techniques and methods exist for the remediation of soil, groundwater and wastewater to meet the clean-up standards. Examples include dig-and-haul, pump-and-treat, biodegradation, sparging, and vapor extraction. However, meeting stringent clean-up standards is often costly, time-consuming, and often ineffective for many compounds that are recalcitrant, i.e., not responsive to such treatment. Such drawbacks are particularly true of techniques that require contaminated areas to be removed prior to treatments, i.e., ex situ methods, such as is dig-and-haul and pump-and-treat methods. Accordingly, there is a need for an effective method and composition for remediation that treats contaminates in place, i.e., in situ, and does not require movement or prior extraction of the contaminated environmental media prior to treatment.
Aside from the particular physical techniques employed in remediation, chemical oxidation, using traditional oxidation methods or advanced oxidation processes (AOPs), is one remediation approach employed to treat organic contaminants with strong oxidizing chemicals for the purpose of complete mineralization or conversion of such organic contaminants to carbon dioxide and water.
For example, the use of hydrogen peroxide, and in particular metal-activated hydrogen peroxide, often referred to as Fenton's chemistry, has previously been employed in field application of chemical oxidation remediation to produce hydroxyl radicals that are relatively strong oxidants. Metals and chelated metals have also been utilized to catalyze the formation of such hydroxyl radicals, which are capable of destroying a wide range of contaminants. Other catalyzation methods have also been developed with the same goal of forming free radicals capable capable of destroying a wide range of contaminants. These types of oxidation processes have previously been used in both remediation and wastewater treatment systems.
In addition to the general oxidation chemistries described above, the use of persulfate salts for the removal of organic contaminants is also well known. Various methods have also been designed to improve the performance of persulfate salts using a number of various catalytic systems for soil and groundwater remediation and may be applied both in situ and ex situ.
One short coming of such current remediation techniques is that the treatment and remediation of compounds that are either partially or completely immiscible with water, i.e., Non Aqueous Phase Liquids or “NAPLs”, has shown to be particularly difficult. Similarly, treatment of highly soluble but biologically stable organic contaminants such as MTBE and 1,4-dioxane have also been shown to be quite difficult with conventional remediation technologies and wastewater treatment. This is particularly true if these compounds are not significantly naturally degraded, either chemically or biologically, in soil environments or biological reactors. Accordingly, despite prior advancements, an improved remediation method and composition is needed to remediate such contaminants.
In addition to the oxidative chemistries, activated carbon has become a popular option for the removal of various compounds both inorganic and organic. However, treatments involving activated carbon tend to be expensive due to the high cost of activated carbon itself. Accordingly, a non-cost prohibitive remediation additive with functional characteristics that are at least similar if not superior to that of activated carbon is needed.
As an alternative to activated charcoal, biochar has been shown to be an effective ex situ treatment for various contaminants such as agricultural runoff containing nitrates, phosphates, and ammonia, mine drainage and tailings containing various heavy metals and low pH, municipal storm water, general heavy metals removal and general organic compounds. To this end, biochar has the potential to be an effective environmental remediation tool for the remediation of contaminated soil and groundwater, whether by itself, embedded, or in conjunction with other treatments such as, reductive remediation methods (ZVM) and/or carbon sources, biological (microbial and/or nutrients) remediation methods, metal stabilization methods or combinations thereof occurring simultaneously or sequentially and the delivery of such systems by injection methods.
However, the need to introduce such material into subsurface contaminated areas for use in situ method remediation has been prohibitive of using biochar in such applications. Accordingly, there is still need for a composition and method for effectively introducing biochar into subsurface contamination areas for use in oxidative remediation of organic based contaminants.